1. Field of the Invention
The present invention relates to an apparatus and method for calculating vibration displacement of vibrator, and more particularly, to an apparatus and method for calculating vibration displacement of a vibrator capable of accurately measuring vibration displacement of a vibrator.
2. Description of the Background Art
In general, a vibration displacement sensor for sensing displacement of a vibrator by using an optical device is commonly used for washing machines. The washing machines are mechanical devices for washing the laundry by performing washing, rinsing and dehydrating strokes. Recently, convenience in usage of a washing machine, as well as a cleaning function, is a critical factor for consumers to determine purchase of a product.
In order to increase convenience of usage, developments of products have been accelerated, and especially, a drum-type washing machine for washing the laundry without damage receives much attention in the market.
FIG. 1 is a sectional view showing the structure of a general drum-type washing machine.
As shown in FIG. 1, the general drum-type washing machine includes: a tub 14 installed inside a main body 11 and fixed by springs 12 and dampers 13; a drum 15 installed at the inner side of the tub 14; and a driving motor 16 for rotating the drum 15.
In the general drum-type washing machine, the drum 15 is rotated by more than 1000 times per minute, whereby a dehydration stroke is performed by using a centrifugal force. At this time, however, the laundry in the drum 15 may be inclined to one side, so severe oscillation can be transferred to the tub 14 and the main body 11 and big noise can be generated.
Such vibration of the drum-type washing machine much degrades efficiency of the dehydration stroke, so a method for accurately sensing the amount of generated vibration to solve the inclination phenomenon of the laundry according to the amount of vibration is required.
Currently, in order to sense the generated vibration, a safety switch or a Colpitts resonance circuit is commonly used, which will now be described with reference to FIGS. 2 and 3.
FIG. 2 shows a principle for sensing vibration by using the safety switch in accordance with a conventional art.
As shown in FIG. 2, in the conventional method using the safety switch, as vibration of the tub is increased, one side of the safety switch 21 is hit. Thus, the other side of the safety switch 21 connected to the spring is turned counterclockwise in order to make the two contacts 23 and 24 short, or turned clockwise in order to make two contacts open, whereby abnormal vibration of the tub 14 is sensed.
However, the conventional method using the safety switch is advantageously simple in its structure, but disadvantageous in that the amount of vibration cannot be accurately sensed and a trouble occurs due to mechanical weakness, difficulty in installation, defective contacts or degradation of a restoring force of the spring.
FIG. 3 shows a principle for sensing vibration by using the Colpitts resonance circuit in accordance with the conventional art.
As shown in FIG. 3, the conventional system using the Colpitts resonance circuit includes: a bobbin 31 having a movement path with a certain length; a magnetic core 32 moving inside the bobbin according to vibration applied from outside; and a coil 33 wound outside the bobbin so change inductance according to the magnetic core 32.
In the conventional method using the Colpitts resonance circuit, when inductance of the coil 33 is changed according to positions of the magnetic core 32, frequency of the Colpitts resonance circuit is changed. Thus, by detecting the amount of the changed inductance, an amount of vibration corresponding to the detected amount of inductance is measured.
However, the conventional method using the Colpitts resonance circuit is advantageous in that its structure is simple but because the amount of change in the inductance is so small that a circuit is required to amplify the changed amount of inductance and detect a resonance frequency in order to accurately measure the amount of vibration. This results in a high cost and the washing machine needs to be accurately leveled in order to perform an optimum function of the Colpitts resonance circuit.
As mentioned above, the conventional vibration displacement calculating method, which uses the safety switch or the Colpitts resonance circuit to measure the amount of vibration, fails to accurately sense the amount of vibration.